diff --git a/doc/userguide/rules/header-keywords.rst b/doc/userguide/rules/header-keywords.rst index e28b14e283..a6837d73cf 100644 --- a/doc/userguide/rules/header-keywords.rst +++ b/doc/userguide/rules/header-keywords.rst @@ -711,6 +711,12 @@ Example of icmp_seq in a rule: alert icmp $EXTERNAL_NET any -> $HOME_NET any (msg:"GPL SCAN Broadscan Smurf Scanner"; dsize:4; icmp_id:0; :example-rule-emphasis:`icmp_seq:0;` itype:8; classtype:attempted-recon; sid:2100478; rev:4;) +.. note:: Some pcap analysis tools, like wireshark, may give both a little + endian and big endian value for ``icmp_seq``. The ``icmp_seq`` keyword + matches on the big endian value, this is due to Suricata using the network + byte order (big endian) to perform the match comparison. + + icmpv4.hdr ^^^^^^^^^^